Computer storage system providing virtualized storage

• US 7,120,673 B2
• Filed: 11/16/2001
• Issued: 10/10/2006
• Est. Priority Date: 05/18/2000
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Kitamura, Manabu, Arai, Kouji
• Primary Examiner(s): Dharia, Rupal
• Assistant Examiner(s): Gillis, Brian J.
• Application Number:
  US09/991,219
• Publication Number:
  US 20030212854A1
• Time in Patent Office: 1,789 Days
• Field of Search: 709/213, 709/214, 709/215, 709/221, 711/112, 711/111
• US Class Current: 709/213
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

In the computer system where the plurality of host computers and the plurality of storage apparatuses are interconnected, in order to carry out the data migration between the storage apparatuses transparently to the host computers, the back end server provides the virtual disk to the host computers. From the host computers, at first, the virtual disk looks the same as the old storage subsystem. When migrating the data from the old storage subsystem to the new storage subsystem, at first, the back end server instructs the data migration unit to execute the data migration processing. Subsequently, the back end server switches the setting of the virtual disk, thereby causing the virtual disk to correspond to the new storage subsystem.

Claims

1. A storage server for providing a virtualized storage subsystem accessible by a plurality of hosts, the storage server comprising:

a first communication interface coupled with a first network switch to receive at least one data access request requesting an access to the virtualized storage subsystem from one of the hosts that is coupled with the network switch;

a second communication interface coupled with a second network switch to communicate with a first and a second storage subsystem including first and second storage areas, respectively, to store data associated with the access requesting host, the first and second storage subsystems being provided at remote locations from the storage server; and

a virtual device driver component that is operable to present a virtual storage area of the virtualized storage subsystem to the access requesting host, the virtual storage area being mapped to the first storage area of the first storage subsystem prior to migration of data from the first storage subsystem to the second storage subsystem,

wherein the storage server is configured to receive, from the access requesting host, a first data access request requesting reading of data stored in the virtualized storage subsystem, the first data access request including a storage address identifying a first location in the virtual storage area of the virtualized storage subsystem, to generate a second data access request directed to the first storage subsystem, the second data access request including a storage address identifying a second location in the first storage area that is mapped to the first location in the virtual storage area of the virtualized storage subsystem, to copy the data received from the first storage subsystem to a third location in the second storage area of the second storage subsystem, and to send the received data to the access requesting host, and

wherein the storage server is configured to change mapping of the first location in the virtual storage area of the virtualized storage subsystem from the second location in the first storage area to the third location in the second storage area so that the access requesting host accesses the first storage subsystem and the second storage subsystem through the storage server.

2. The storage server of claim 1 wherein if the storage server receives, from the access requesting host, a third data access request including the storage address identifying the first location in the virtual storage area of the virtualized storage subsystem after the copying of the data, the storage server is configured to generate a fourth data access request directed to the second storage subsystem, the fourth data access request including a storage address identifying the third location in the second storage area.

3. The storage server of claim 1, wherein the first and second network switches are the same.

4. The storage server of claim 1, wherein the storage server is configured to initiate migration of data that has not been copied from the storage area of the first storage subsystem to the storage area of the second storage subsystem, while stopping data access operation from the hosts to the virtualized storage subsystem.

5. The storage server of claim 1, wherein when the storage server receives, from the access requesting host, a data access request requesting an access to a portion of the data stored in the first storage area while the data stored in the first storage area is migrated to the second storage area, the storage server accesses a data migration unit to determine whether the data access request should be directed either to the first storage subsystem or the second storage subsystem, with the data migration unit maintaining a record on portions of the data stored in the first storage area that remain in the first storage area while the data stored in the first storage area is migrated to the second storage area.

6. The storage server of claim 5, wherein the data migration unit is provided in one of the first and second storage subsystems or the storage server.

7. A storage system coupled with a network switch, comprising:

a backend server coupled with a plurality of hosts via a network;

a first storage subsystem including a first storage controller and a plurality of first storage devices, the first storage controller configured to control access to the first storage devices, the first storage devices defining a first storage area, the first storage subsystem being coupled with the backend server via the network; and

a second storage subsystem including a second storage controller and a plurality of second storage devices, the second controller configured to control access to the second storage devices, the second storage devices defining a second storage area, the second storage subsystem being coupled with the backend server via the network,

wherein the backend server, the first storage subsystem, and the second storage subsystems are all remotely located from each other,

wherein the backend server presents a virtualized storage subsystem to the hosts, the virtualized storage subsystem including a virtual storage area being mapped to the first storage area of the first storage subsystem prior to migration of the data from the first storage subsystem to the second storage subsystem,

wherein the backend server is configured to receive, from the host, a first data access request requesting reading of data stored in the virtualized storage subsystem, the first data access request including a storage address identifying a first location in the virtualized storage area of the virtualized storage subsystem, and to generate a second data access request directed to the first storage subsystem, the second data access request including a storage address identifying a second location in the first storage area that is mapped to the first location in the virtualized storage area of the virtual storage subsystem, to copy the data received from the first storage subsystem to a third location in the second storage area of the second storage subsystem, and to send the received data to the host, and

wherein the backend server is configured to change mapping of the first location in the virtualized storage area of the virtualized storage subsystem from the second location in the first storage area to a third location in the second storage area so that the host accesses the first storage subsystem and the second storage subsystem through the backend server.

8. A method for operating a storage system with a virtualized storage subsystem, the method comprising:

receiving a first data access request from a first host at a backend server, the first data access request requesting reading of data stored in a virtualized storage subsystem, the backend server being coupled with a plurality of hosts and first and second storage subsystems via a network, the backend server presenting the virtualized storage subsystem to the plurality of the hosts, the first data access request including a storage address identifying a first location in a virtual storage area of the virtualized storage subsystem, the first and second storage subsystems being located remotely from the backend server;

generating a second data access request at the backend server, the second data access request including a storage address identifying a second location in a first storage area that is mapped to the first location in the virtual storage area, the first storage area being defined by the first storage subsystem;

transmitting the second data access request to the first storage subsystem to copy data corresponding to data requested by the first data access request from the second location to a third location in the second storage area of the second storage subsystem;

sending the copied data to the host; and

changing mapping of the first location in the virtual storage area of the virtualized storage subsystem from the second location in the first storage area to the third location in the second storage area in connection with copying the data from the second location to the third location, the second storage area being defined by the second storage subsystem.

9. The method of claim 8, further comprising:

maintaining a table holding a flag for indicating a state of copying on each data block associated with the virtual storage area.

10. The method of claim 9, wherein the table is maintained by one of the first and second storage subsystems.

11. The method of claim 10, further comprising:

receiving a third data access request at the backend server including the storage address identifying the first location of the virtual storage area of the virtualized storage subsystem from a second host after the copying of the data; and

generating, by the backend server, a fourth data access request directed to the second storage subsystem, the fourth data request including a storage address identifying the third location in the second storage area.

12. The method of claim 11, wherein the first and second hosts are different hosts.

13. The method of claim 8, wherein each data block corresponds to a logical block address.

14. A storage server for providing a virtualized storage subsystem accessible by a plurality of hosts, the storage server comprising:

a first communication interface coupled with a network switch to receive a data access request requesting an access to the virtualized storage subsystem from one of the hosts that is coupled with the network switch;

a second communication interface coupled with the network switch to communicate with first and second storage subsystems including first and second storage areas, respectively, to store data associated with the access requesting host; and

a virtual device driver component that is operable to present a virtual storage area of the virtual storage subsystem to the access requesting host, the virtual storage area being mapped to the first storage area of the first storage subsystem prior to migration of data from the first storage subsystem to the second storage subsystem,

wherein the storage server is configured to receive, from the access requesting host, a first data access request requesting reading of data stored in the virtualized storage subsystem, the first data access request including a storage address identifying a first location in the virtual storage area of the virtualized storage subsystem, to generate a second data access request directed to the first storage subsystem, the second data access request including a storage address identifying a second location in the first storage area that is mapped to the first location in the virtual storage area of the virtualized storage subsystem, to copy the data received from the first storage subsystem to a third location in the second storage area of the second storage subsystem, and to send the received data to the access requesting host,

wherein the storage server is configured to change mapping of the first location in the virtual storage area of the virtualized storage subsystem to the third location in the second storage area so that the access requesting host accesses the first storage subsystem and the second storage subsystem through the storage server,

wherein if the storage server receives, from the access requesting host, a third data access request including the storage address identifying the first location in the virtual storage area of the virtualized storage subsystem via the first interface after copying of the data, the storage server is configured to generate a fourth data access request directed to the second storage subsystem and to send the fourth data access request to the second storage subsystem via the second interface, the fourth data access request including a storage address identifying the third location in the second storage area.

15. The storage server of claim 14, wherein the server is configured to initiate migration of data that has not been copied from the storage area of the first storage subsystem to the storage area of the second storage subsystem via the second interface, while stopping data access operation from the hosts to the virtualized storage subsystem.